LAG CAMERA: A MOVING MULTI-CAMERA ARRAY FOR SCENE ACQUISITION

Daniel G. Aliaga, Yi Xu and Voicu Popescu

Many applications, such as telepresence, virtual reality, and interactive walkthroughs, require a three-dimensional (3D) model of real-world environments. Methods, such as lightfields, geometric reconstruction and computer vision use cameras to acquire visual samples of the environment and construct a model. Unfortunately, obtaining models of real-world locations is a challenging task. In particular, important environments are often actively in use, containing moving objects, such as people entering and leaving the scene. The methods previously listed have difficulty in capturing the color and structure of the environment while in the presence of moving and temporary occluders. We introduce a new class of cameras called lag cameras. The main concept is to generalize a camera to take samples over space and time. Such a camera, can easily and interactively detect moving objects while continuously moving through the environment. Moreover, since both the lag camera and occluder are moving, the scene behind the occluder is captured by the lag camera even from viewpoints where the occluder lies in between the lag camera and the hidden scene. We demonstrate an implementation of a lag camera, complete with analysis and captured environments.

LP FITTING APPROACH FOR RECONSTRUCTING PARAMETRIC SURFACES FROM POINTS CLOUDS

Thibault Marzais, Yan Gerard and Rémy Malgouyres

We present a method to reconstruct a surface from a group of points, each one given with two parameters. The kind of reconstructed surface can be a Bezier surface, a B-spline surface or any surface generated by a basis of functions. The usual method involved in such a reconstruction is the least squares approach. Our original fitting method called LP-fitting uses a linear program for minimizing the uniform error instead of the quadratic error considered in least squares. Experimental results comparing both approaches show that the surface obtained by LP-fitting is usually closer (from a uniform point of view) from the the initial points cloud than the surface obtained by least squares.

ADAPTIVE LEVEL OF DETAIL WITH OCCLUSION CULLING

Hermann Birkholz and Stefan Rahn

Many techniques have been developed in order to accelerate the visualization of large triangle meshes. Level of Detail techniques can be used to create view-dependent approximations of wide range scenes with low occlusion, such as landscapes. For highly occludes scenes there exist many occlusion culling techniques, which cull occluded parts of the scene before rendering. This can drastically speed up the visualization of such scenes but wont improve rendering of wide non occluded scenes. In this paper we will combine both acceleration methods. We present a new approach, which combines the benefits of Level of Detail rendering and of Occlusion Culling, in order to minimize their drawbacks. The technique adds occlusion as a view-dependence criterion for Level of Detail rendering and is even able to optimize the refinement of self occluding meshes.

A GEOMETRIC REPRESENTATION FOR THE REAL-TIME SIMULATION OF NC MACHINING PROCESSES

Aitor Moreno, Carlos Toro, Iosu Arizkuren, Alvaro Segura, Jorge Posada, Marcelino Novo, Juanjo Falcón and Nieves Alcaín

In this paper we present a level-based representation used in the implementation of a real-time material removal simulator, whose principal feature is to be embedded into a commercial NC machine where the hardware capabilities are limited. The representation and its supporting architecture is used for the generation of an interactive simulation of the actual machined part taking as input the NC machine feedback with the following features: i) The virtual and real simulations must be synchronized, ii) the internal representation of the objects must be as exact and accurate as possible and iii) the graphical quality should be acceptable, taking into account the graphics hardware restrictions (12” monitor, 800x600 pixels, with simple hardware acceleration). The mentioned representation was implemented in the frame of a research project, allowing the evaluation of the architecture with some results presented in this paper. The results confirm the hypothesis that the current implementation simulates low and medium complexity models synchronously. More complex models require some tuning of the simulation parameters in order to be correctly simulated.

ADAPTIVE CONSTRAINT AND 3D SKETCH-BASED DEFORMATION FOR INTERACTIVE FREE FORM SURFACE STYLING

Li Han, Raffaele De Amicis and Giuseppe Conti

This paper tries to answer to the increasing demand in the domain of conceptual design for more intuitive methods for creating and modifying free-form curves and surfaces. This is done by addressing the issue of physical-based shape control by free hand spline sketching instead of the tedious mathematical parameters adjustment. We present a novel approach capable of matching the designer’s requirements in terms of quality and accuracy of the produced model. The algorithm adopts a simple 3D sketching technique and a finite element deformation method to create free-form models. In the method proposed the user applies interactive sculpting to modify a surface in a predicable way. Our algorithm automatically extracts the key points from sketched target curve and adaptively distributes the external-force constraints which impose the force energy on the corresponding control vertexes along their normal. We have limited the influence of these constraints to a localized area by attaching an influence factor to each control vertex of the parent surface. The smoothing function introduced later further solves the transition interval and it provides for symmetry features. This proposed method is finally implemented in a 3D scene environment and the results show how the designers intuitively and exactly control the shape of the surface.

DISCRETE TOOLS FOR VIRTUAL SCULPTURE

Xavier Heurtebise and Sébastien Thon

In a virtual sculpture project, we represent the matter to be sculpted as a set of volume elements (voxels). Sculpture operations of subtraction and addition are applied on these voxels with tools with various shapes and sizes. A major advantage of our system is that sculpted objects can then be used as new tools, because the same model is used for both objects and tools. This is a multiresolution model based on a 3D wavelet transform. We take advantage of the levels of details to speed up display and sculpture. However, using discrete models for objects and tools leads to three problems: important computation time, aliasing when tools are rotated, and how to perform sculpture operations between discrete objects and tools with different orientations and sizes. In this paper, we describe our model and then propose solutions to these problems that allow real-time performance.

COLLABORATION ON SCENE GRAPH BASED 3D DATA

Lorenz Ammon and Hanspeter Bieri

Professional 3D digital content creation tools, like Alias Maya or discreet 3ds max, offer only limited support for a team of artists to work on a 3D model collaboratively. We present a scene graph repository system that enables fine-grained collaboration on scenes built using standard 3D DCC tools by applying the concept of collaborative versions on a general attributed scene graph. Artists can work on the same scene in parallel without locking out each other. The artists' changes to a scene are regularly merged to ensure that all artists can see each others progress and collaborate on current data. We introduce the concept of indirect changes and indirect conflicts to systematically inspect the effects that collaborative changes have on a scene. Inspecting indirect conflicts helps maintaining scene consistency by systematically looking for inconsistencies at the right places.

USING RAY INTERSECTION FOR DUAL ISOSURFACING

Jaya Sreevalsan-Nair, Bernd Hamann and Lars Linsen

Isosurface extraction using ``dual contouring'' approaches have been developed to generate a surface that is ``dual'' of the isosurfaces generated using marching cubes (MC) method. These approaches address some shortcomings of the MC methods including feature-detection within a cell and better triangles. One approach for preserving ``sharp features'' within a cell is to determine isosurface points inside each cell by minimizing the quadric error functions (QEF). However, this category of methods is constrained in certain respects such as finding just one isosurface point per cell or requiring ``Hermite'' data to calculate an isosurface. We present a simple method based on the MC method and the ray intersection technique to compute isosurface points in the cell interior. One of the advantages of our method is that it does not require Hermite data, i.e., the discrete scalar values at vertices suffice. We compute ray intersections to determine isosurface points in the interior of each cell, and then perform a complete analysis of all possible configurations to generate a look-up table for all configurations. Since complex features (e.g., tunnels) tend to be undersampled with ``dual'' points sufficient to represent sharp features and disjoint surfaces within the cell, we use the look-up table to optimize the ray intersection method to obtain minimum number of points necessarily sufficient for defining topologically correct isosurfaces in all possible configurations. The points are further connected using a simple strategy.

SILHOUETTE DETECTION FOR ADAPTIVE POLYGONAL MESH SIMPLIFICATION USING DISTANCE TRANSFORMS

Susana Mata, Luis Pastor and Angel Rodríguez

Distance Transforms have proven to be useful for many image processing applications. Nevertheless, the have only recently started to be used in computer graphics environments. The goal of this paper is to propose a new technique based on Distance Transforms for detecting mesh elements which are close to the objects' external contour (from a given point of view), and using this information for weighting the approximation error which will be tolerated during the mesh simplification process.

SIMPLE AND EFFICIENT TOOLS FOR VIRSCULPT

Romain Raffin, Guillaume Thibault and Gilles Gesquière

Numerous papers are describing methods for virtual sculpture which simulate real behaviours in a virtual environment. During the sculpture process, the artist does not have to be disturbed by the latency of an interaction between the object he works on and the tool he uses. Existing data structures or multiprocessing enhancements are first ways to overcome this problem. We choose to focus our work on the interaction between an object and a tool in order to improve the modelling process, even if the data model used is kept simple.

SURFACE CONSTRUCTION USING TRICOLOR MARCHING CUBES

Shaojun Liu, Jia Li and Xiaojun Jing

This paper presents a new marching cubes (MC) method for 3D surface construction. The proposed method allows cell vertex whose value equal the threshold lie on the surface. The simulation results show that our solution gives good results.

A COMPARISON OF CYLINDRICAL PASTING METHODS

Shalini Aggarwal and Stephen Mann

In this paper, we study six different boundary control point mappings for cylindrical surface pasting and compare the resulting pasted surfaces for $C^0$ join continuity. All six methods are algorithmically simple with low computational costs, requiring minimal computation aside from surface evaluation. The results demonstrate an order of magnitude quality improvement for some of our methods on a convex-only curved base, however, as the complexity of the base surface increases all methods show similar performance.

DATA PROCESSING AND COMPACT REPRESENTATION OF MEASURED ISOTROPIC SPECTRAL BRDF

Huiying Xu

This paper presents the methods for both data processing and compact representation of measured isotropic spectral BRDF. For the data processing, we develop a numerical method for filtering the noises, re-sampling the data from non-uniform sampling to uniform sampling, and interpolation. For the compact representation, we propose a method to represent the spectral BRDF in both the spectral and spatial domains. In spectral domain, for each pair of the incident and outgoing directions, we represent the spectral BRDF with Fourier coefficients. For all the outgoing directions of a given incident direction, we represent the same-order Fourier coefficients either directly using a linear combination of spherical harmonics or a linear combination of spherical harmonics and a Gaussian, depending on their angular dependencies. Three Gaussian expressions are presented. Numerical studies are given for a measured isotropic spectral BRDF.

EFFICIENT RENDERING OF HIGH-DETAILED OBJECTS USING A REDUCED MULTI-RESOLUTION HIERARCHY

Mathias Holst and Heidrun Schumann

In the field of view-dependant continuous level of detail of triangle-meshes it is often necessary to extract the current LOD triangle for triangle. Thus, triangle strips are only of very limited use, or only usable with a high effort. In this work a method is proposed that allows a stepwise reduction of a highly graduated LOD hierarchy by merging nodes. The result of this process is a reduced hierarchy, which allows the extraction of many neighbored static triangles in one step, so that triangle strips are applicable more efficiently. We show that this results in a significant decimation of processed vertices.

AN INTERACTIVE METHOD FOR REFRACTIVE WATER CAUSTICS RENDERING USING COLOR AND DEPTH TEXTURES

Nuttachai Tipprasert and Pizzanu Kanongchaiyos

Realistic rendering of underwater scenes is one of the most anticipates research topics in computer graphics. Caustics are the important component enhancing the realism of this kind of scenes. Unfortunately, rendering caustics is a time consuming task, as a result, most existing algorithms cannot handle this at interactive rate. In recent years, the volumetric texture based rendering algorithms has been proposed which can render the underwater scene with caustics in real-time. However, these algorithms require large amount of memory and be restricted to non-complex scene. In this paper we present a new interactive caustics rendering algorithm which require less memory usage. In our proposed method, we represent each object as a pair of color and depth texture. Color texture is used to store the object image viewed from viewing rays which refracted at water surface. We calculate the light intensity distribution on this image and store the result back to the color texture. The depth texture is used in the intensity calculation process to improve accuracy of the caustics patterns. Our experiment shows that proposed algorithm can handle complex underwater scene with caustics at interactive time rate. While using a pair of color and depth in stead of volumetric texture, we can reduce memory usage significantly.

ALGEBRAIC CURVES IN PARALLEL COORDINATES – Avoiding the “Over-Plotting” Problem

Zur Izhakian

Until now the representation (i.e. modeling) of curve in Parallel Coordinates is constructed from the point <--> line duality. The result is a "line-curve" which is seen as the envelope of it's tangents. Usually this gives an unclear image and is at the heart of the "over-plotting" problem; a barrier in the effective use of Parallel Coordinates. This problem is overcome by a transformation which provides directly the "point-curve" representation of a curve. Earlier this was applied to conics and their generalizations. Here the representation, also called dual, is extended to all planar algebraic curves. Specifically, it is shown that the dual of an algebraic curve of degree n is an algebraic of degree at most n(n - 1) in the absence of singular points. The result that conics map into conics follows as an easy special case. An algorithm, based on algebraic geometry using resultants and homogeneous polynomials, is obtained which constructs the dual image of the curve. This approach has potential generalizations to multi-dimensional algebraic surfaces and their approximation. The "trade-off" price then for obtaining planar representation of multidimensional algebraic curves and hyper-surfaces is the higher degree of the image's boundary which is also an algebraic curve in ||-coords.

SURFACE SIMPLIFICATION GUIDED BY MORPH-TARGETS

Uwe Berner and Thomas Rieger

Many effective automatic surface simplification algorithms have been developed. These automatic algorithms create very plausible results in many cases, but at very low levels of detail they do not preserve the visual appearance of the original model very well. This could be improved if surface simplification algorithms were able to make use of semantic or high-level meaning of models. The idea of morph-target-based surface simplification is to use distance information inside the morph-targets to acquire the relative importance of different surface regions without user guidance. Using this additional input the model is simplified by using modified quadric error metrics.

OUT-OF-CORE CONSTRUCTION AND 3D VISUALIZATION OF LEVEL-OF-DETAIL TERRAINS POPULATED WITH LARGE COLLECTION OF HETEROGENEOUS OBJECTS

Anupam Agrawal, M. Radhakrishna and R.C. Joshi

Interactive visualization of very large scale terrain data in scientific visualization, GIS or simulation and training applications is a hard problem. The grid digital terrain elevation and texture data models are not only too large to be rendered in real-time but also exceed physical main memory capacity. Therefore to avoid excessive paging in virtual memory, the terrain data must be maintained on disk and dynamically loaded into main memory as required by the rendering algorithm. Further to bring photorealism in visualization, it is required to place multiple collections of man-made objects such as buildings, lampposts etc. as well as natural objects such as trees, grass etc. on top of the terrain surface. In this paper we have proposed an integrated approach for effective out-of-core visualization of terrains populated with large collection of discrete, static heterogeneous objects. We have developed an efficient tile-based out-of-core view-dependent Level of Detail (LOD) mesh simplification algorithm for real-time rendering of large terrains. Instead of manipulating individual triangles, the algorithm operates on clusters of geometry called blocks of aggregate triangles. Hence the amount of work CPU must perform is greatly reduced. The formation of long triangle strips for LOD blocks also solves the CPU-to-Card bandwidth problem. The tile-based multiresolution terrain geometry framework has been extended to support large geospecific satellite or aerial imagery textures. To display large collection objects over the terrain while maintaining the real-time frame rate, an efficient object handling method has been proposed using paging technique and object instantiation. User is allowed to control the objects locations, scales and orientations. Multitexturing scheme has been employed to blend geotypical detailed textures representing features such as grass or stone with the geospecific imagery. The algorithms have been implemented using Visual C++ and OpenGL 3D API and successfully tested on different real-world height maps and satellite phototextures of sizes upto 16K*16K coupled with thousands of static objects on PCs.

A NEW NON-UNIFORM LOOP SCHEME

Sandrine Lanquetin and Marc Neveu

In this paper, we introduce a new non-uniform Loop scheme. It refines selected areas which are chosen manually or automatically according to the precision of the control mesh compared to the limit surface. Subdivision rules avoid cracks and generate a progressive mesh with a difference of at most one subdivision level between two adjacent faces. Moreover valences of vertices always remain almost regular. Results obtained from our scheme are compared to those of the T-algorithm and the incremental algorithm

POINT CLOUD DENOISING USING ROBUST PRINCIPAL COMPONENT ANALYSIS

Esmeide A. Leal Narváez and Nallig Eduardo Leal Narváez

This paper presents a new method for filtering noise occurring in point cloud sampled data, which smoothes the data set while preserves sharp features. We propose a variant of the principal component analysis method, which instead of using Euclidean distance in inverse proportional weighting with computationally expensive exponential factors, uses the Euclidean distance in the inverse proportional weighting with linear factors. The determination of weighted factors by means of inverse proportional linear repartition makes our variant robust to outliers. Additionally, we propose a simple solution to the problem of data shrinkage produced by the linear local fitting of the principal component analysis. The proposed method is simple, fast to implement, and is shown to be effective when applied to several data set

TERRAIN SYNTHESIS BY-EXAMPLE

John Brosz, Faramarz F. Samavati and Mario Costa Sousa

Synthesizing terrain or adding detail to terrains manually is a long and tedious process. With procedural synthesis methods this process is faster but more difficult to control. This paper presents a new technique of terrain synthesis that uses an existing terrain to synthesize new terrain. To do this we use multi-resolution analysis to extract the high-resolution details from existing models and apply them to increase the resolution of terrain. Our synthesized terrains are more heterogeneous than procedural results, are superior to terrains created by texture transfer, and retain the large-scale characteristics of the original terrain.

PRECISE MODELING OF ARCHEOLOGICAL ARTIFACTS

Junta Doi, Wataru Sato, Masahiko Hoshi, Shinji Morishita, Tomohiro Morita, Kota Sudo and Youhei Nakanishi

Precise shape reconstruction of archeological artifacts within 0.01 mm 3D resolutions are reported based on our proposal of a practical, accurate, topologically robust and ranging error resistive shape modeling procedure that approximates a real 3D object, with the matrix-format data structure, for the resulting shape processing. Examples of the shape processing are based on the premise of the virtual manipulation of the 3D shape. Radial distance of each scanning point is measured by laser triangulation. A face array listing, which defines the sampling point connectivity and the shape of the mesh, is assigned to meet the desired meshing. Topologically stable meshing, and hence, an accurate approximation, free from the shape ambiguity unavoidable in the so-called ICP (Iterative Closest Point) modeling, is then accomplished. This proposal allows not only the precise shape modeling, but also virtual shape manipulation for various trainings and restorations.

MESH RETRIEVAL BY COMPONENTS

Ayellet Tal and Emanuel Zuckerberger

This paper examines the application of the human vision theories of Marr and Biederman to the retrieval of three-dimensional objects. The key idea is to represent an object by an attributed graph that consists of the object's meaningful components as nodes, where each node is fit to a basic shape. A system that realizes this approach was built and tested on a database of about 400 objects and achieves promising results. It is shown that this representation of 3D objects is very compact. Moreover, it gives rise to a retrieval algorithm that is invariant to non-rigid transformations and does not require normalization.

IMAGE MATCHING USING RELATIONAL GRAPH REPRESENTATION

Lai Chui Yen, Daut Daman and Mohd Shafry Mohd Rahim

It has been suggested that in many applications one is better advised to extract structural descriptions from the image first. Here, we proposed a stereo matching strategy that involves the usage of structural description from the image. This structural matching strategy is to address the problem of image features undergo occlusion and also the missing feature situation. The description of the image scene was made by constructing a relational graph that described the relationship among image primitives. Consequently, the matching becomes the problem of finding a match between two structural descriptions, which is represented by relational graph. The matching between these relational graphs was determined by comparing these structures using a graph theoretical approach. The best available match between relational graphs can be determined by finding the best maximal clique in an association graph

EMPOWERING ISO-SURFACES WITH VOLUME DATA

Danilo Medeiros Eler, Patrícia Shirley Herrera Cateriano, Luis Gustavo Nonato, Maria Cristina Ferreira de Oliveira and Haim Levkowitz

Surface rendering algorithms are fast, but not suited to applications that demand exploration of internal volume structures, as such information is lost in conventional surface rendering. In this article we introduce an enhanced surface rendering algorithm - named VoS, Volume on Surface - that supports visualization of internal volume structures. VoS integrates surface and volume rendering approaches into an efficient framework for interactive visualization of volume information. A ray casting is performed to map volume information onto the boundary faces of a surface extracted from the volume grid, enabling the display of structures internal to the surface. As such, the technique exploits the advantages of surface rendering while keeping the volumetric information. VoS thus offers a low-cost alternative to volume rendering in some practical situations, as its resulting surfaces can be rendered on commodity graphics hardware at interactive rates. Moreover, a user can easily fine tune the color and opacity transfer function definitions, because changes in the transfer functions are handled at the rendering step, rather than at the costly ray-casting operation.

A SYSTEMATIC APPROACH TO MULTIPLE DATASETS VISUALIZATION OF SCALAR VOLUME DATA

Gaurav Khanduja and Bijaya B. Karki

Many applications require simultaneous display of multiple datasets, representing multiple samples, or multiple conditions, or multiple simulation times, in the same visualization. Such multiple dataset visualization (MDV) has to handle and render massive amounts of data concurrently. We analyze the performance of two widely used techniques, namely, isosurface extraction and texture-based rendering for visualization of multiple sets of the scalar volume data. Preliminary tests performed using up to 25 sets of moderate-sized (256^3) data show that the calculated times for the generation and rendering of polygons representing isosurface, and for the mapping of a series of textured slices increase non-uniformly with increasing the number of individual datasets. Both techniques are found to no longer be interactive with the frame-rates dropping below one for six or more datasets. To improve the MDV frame-rate, we propose a scheme based on the combination of hardware-assisted texture mapping and general clipping. In essence, it exploits the 3D surface texture mapping by rendering only the externally visible surfaces of all volume datasets at a given instant, with dynamic clipping enabled to explore the interior of the data. The calculated frame-rates remain above one and are substantially higher than those with the other two techniques.

A PROGRESSIVE REFINEMENT APPROACH FOR THE VISUALISATION OF IMPLICIT SURFACES

Manuel N. Gamito and Steve C. Maddock

Visualising implicit surfaces with the ray casting method is a slow procedure. The design cycle of a new implicit surface is, therefore, fraught with long latency times as a user must wait for the surface to be rendered before being able to decide what changes should be introduced in the next iteration. In this paper, we present an attempt at reducing the design cycle of an implicit surface modeler by introducing a progressive refinement rendering approach to the visualisation of implicit surfaces. This progressive refinement renderer provides a quick previewing facility. It first displays a low quality estimate of what the final rendering is going to be and, as the computation progresses, increases the quality of this estimate at a steady rate. The progressive refinement algorithm is based on the adaptive subdivision of the viewing frustrum into smaller cells. An estimate for the variation of the implicit function inside each cell is obtained with an affine arithmetic range estimation technique. Overall, we show that our progressive refinement approach not only provides the user with visual feedback as the rendering advances but is also capable of completing the image faster than a conventional implicit surface rendering algorithm based on ray casting.

RELIABLE COMPUTATION OF ROOTS TO RENDER REAL POLYNOMIALS IN COMPLEX SPACE

J. F. Sanjuan-Estrada, L. G. Casado and I. García

Many geometric applications involve computation and manipulation of non-linear algebraic primitives. These basic primitives like points, curves and surfaces are represented using real numbers and polynomial equations. For example, ray tracing technique rendering three-dimensional realistic images, where each pixel need to find the minimum positive root of intersection point when a lineal ray hit a surface. However, the intersection between a ray and a polynomial equation has differents roots, where each root can be a real number (without imaginary part) or a complex number (with real and imaginary part), so that, the number of roots is equal to degree of polynomial. In this paper, we extend the traditional ray tracing technique to show roots in the complex space. We use an algorithm that analyse all verified roots of intersection point using interval arithmetic. This algorithm computes verified enclosures of the roots of a polynomial by enclosing the zeros in narrow bounds. The reliability of the algorithm depends on the accurate evaluation of these complex roots. Finally, we propose differents solutions to render a image in the complex space, where the arguments of complex roots are used to choose the roots of intersection point in complex space, while the color of each pixel is computed by minimum modulus of complex roots chosen.

LOCAL CONTROL FOR TEMPORAL EVOLUTION OF TEXTURED IMAGES

Francesca Taponecco

We present a novel algorithm that allows producing varying textures. The basic pattern of the texture is given by an example and by a vector control field that defines how anisotropic textures have to be adapted and deformed locally. By changing this vector control field over time, animations and variations of the texture can be generated. The method is simple, general and allows managing control and manipulation. Significant applications can be found in producing textures in motion, in generating dynamic features' variation in non-homogeneous textures, and, especially, in visualizing time-varying image-based rendered flow fields for scientific visualization.

AN INCREMENTAL WEIGHTED LEAST SQUARES APPROACH TO SURFACE LIGHTS FIELDS

Greg Coombe and Anselmo Lastra

An Image-Based Rendering (IBR) approach to appearance modelling enables the capture of a wide variety of real physical surfaces with complex reflectance behaviour. The challenges with this approach are handling the large amount of data, rendering the data efficiently, and previewing the model as it is being constructed. In this paper, we introduce the Incremental Weighted Least Squares approach to the representation and rendering of spatially and directionally varying illumination. Each surface patch consists of a set of Weighted Least Squares (WLS) node centers, which are low-degree polynomial representations of the anisotropic exitant radiance. During rendering, the representations are combined in a non-linear fashion to generate a full reconstruction of the exitant radiance. The rendering algorithm is fast, efficient, and implemented entirely on the GPU. The construction algorithm is incremental, which means that images are processed as they arrive instead of in the traditional batch fashion. This human-in-the-loop process enables the user to preview the model as it is being constructed and to adapt to over-sampling and under-sampling of the surface appearance.

REAL-TIME IMAGE BASED LIGHTING FOR OUTDOOR AUGMENTED REALITY UNDER DYNAMICALLY CHANGING ILLUMINATION CONDITIONS

Tommy Jensen, Mikkel S. Andersen and Claus B. Madsen

Knowledge about illumination conditions in a real world scene has many applications, among them Augmented Reality which aims at placing virtual objects in the real world. An important factor for convincing augmentations is to use the illumination of the real world when rendering the virtual objects so they are shaded consistently and cast consistent shadows. The work presented in this paper aims at making robust system capable of estimating the lighting of an outdoor scene, and apply the light changes to the virtual augmented objects that are placed within a real scene. The method uses an Irradiance Volume, modified to use an environment map of a given scene, to mimic the multiple lights reflected in a scene using Image Based Lighting, while normal Phong shading is used to mimic the sun shading. These are combined with a Shadow Volume method to ensure shadow interaction with the surrounding environment. For every frame an Illumination Estimation approximates local illumination light parameters used in the rendering of the augmented objects. The light parameters are furthermore used to, at runtime, create new environment maps, to update the irradiance volume. The result is a rendering pipeline capable of handling dynamic light changes, and applying them to augmented objects within a given scene, enabling realistic augmentations under changing illumination conditions.

SIMPLE AND FAST RAY TRACING OF POINT-BASED GEOMETRY

Nordin Zakaria, Bahari Belaton and Abdullah Zawawi Hj Talib

We discuss in this paper a framework for simple and fast ray tracing of point-based geometry. Our solution requires neither implicit surface definition nor the use of non-simple rays. Points are simply treated as disk primitives. To prevent shading artifacts due to the use of disk representation, each ray is intersected with a few disks, and the intersection results interpolated. Further, to speed up the ray-object search, we adapt the KD-tree with bounding spheres structure applied in the QSplat point splatting system (Rusinkiewicz and Levoy 2000). Our prototype implementation is generally competitive compared to previous point set ray tracers. Further it demonstrates considerable speedup over a point set ray tracer based on a conventional KD-tree, while producing images with acceptable ray-traced quality.

PROGRESSIVE TRANSMISSION AND RENDERING OF FOVEATED VOLUME DATA

Chen Chen, Zhiyong Huang, Hang Yu and Ee-Chien Chang

With development of biomedical and networking technology, interactive volume rendering with data transmitted via the network becomes an interesting topic. Two technical problems are data transmission and fast volume rendering. In this paper, two schemes using wavelet foveation are proposed and implemented: the region-based and coarse-to-fine. The first scheme transmits and renders the region of interest (ROI) of volume data on the client site at highest resolution for the first time, and consequently it iteratively expands the region layer by layer towards to the peripheral. While the second one gives a complete image in a low resolution for the first time on the client. The detail coefficients will be transmitted continuously and the rendering result will be progressively refined depending on the distance to the ROI.

DIFFUSION BASED PHOTON MAPPING

Lars Schjøth, Ole Fogh Olsen and Jon Sporring

Density estimation employed in multi-pass global illumination algorithms give cause to a trade-off problem between bias and noise. The problem is seen most evident as blurring of strong illumination features. In particular this blurring erodes fine structures and sharp lines prominent in caustics. To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features, while eliminating noise. We call our method diffusion based photon mapping.

CINEMA COMICS: CARTOON GENERATION FROM VIDEO STREAM

Won-Il Hwang, Pyung-Jun Lee, Bong-Kyung Chun, Dong-Sung Ryu and Hwan-Gue Cho

This paper presents CORVIS(COmics Rendering system with VIdeo Stream) which creates comics strips from video streams. CORVIS generates a compact comics book from a video streams of a cinema to show an abstract story of the cinema. For this procedure, first we need to select a set of important featuring scenes in a film and transform them into a simplified illustration by Mean-Shift segmentation procedure. Then we insert the stylized comics effects to each illustration cut by considering the before and after video stream images. These stylized effects include the speed lines and rotational trajectory. Next we place the word balloon to show the dialogues of actors. Next, some echoic words e.g., "BANG", will be inserted to the comic cut in a highly transformed form to imitate the sound effects of the original film. We tested our method to the well-known cinemas such as "Spider Man II" and "I ROBOT". The final result shows our technique is very effective and attractive to creating a compact comics booklet from a video streams.

A SURVEY OF IMAGE-BASED RELIGHTING TECHNIQUES

Biswarup Choudhury and Sharat Chandran

Image-based Relighting (IBRL) has recently attracted a lot of research interest for its ability to relight real objects or scenes, for novel illuminations that were captured in natural/synthetic environments. Complex lighting effects such as subsurface scattering, interreection, shadowing, mesostructural self-occlusion, refraction and other relevant phenomena can be generated using IBRL. The main advantage of Image-based Graphics is that the rendering time is independent of scene complexity as the rendering is actually a process of maipulating image pixels, instead of simulating light transport. The goal of this paper is to provide a complete and systematic overview of the research in Image-based Relighting. We observe that essentially all IBRL techniques can be broadly classied into three categories, based on how the scene information is captured: Reectance function based, Basis function based, and Plenoptic function based. We discuss the charecteristics of each of these categories and their representative methods. We also discuss about sampling density and light source type, relevant issues of IBRL.

SKIN MODELING AND RENDERING BASED ON VISUAL PERCEPTION

Azam Bastanfard and Nadia Magnenat Thalmann

Human skin modeling and rendering affected with a variety of cues. These are including human visual perception of skin texture and lighting. An attempt to mimic such attributes by computer is an aspiring goal and challenging task. This paper proposes a novel algorithm with two techniques as a key solution capturing such a variety of cues to skin appearance. The idea is to capture these two characteristics for skin rendering. The first is the skin noise generation that developed in visual perception. The second is skin texture rendering. These techniques discuss the skin noise simulation based on human perception theory and simulate skin noise texture like subtle. Then, the skin is rendered with what we call the Bidirectional Reflectance Distribution Function Texture Magnitude technique. The original contribution and advantages of this paper compared with other proposed methods are simple to implement, reliable and their computations are fast enough for an interactive environment. Experimental results demonstrate our approach with a variety of skin texture generation.

A FLEXIBLE REAL-TIME FRAMEWORK FOR PRE-CALCULATED GLOBAL ILLUMINATION SOLUTIONS

Markus Lipp, Stefan Maierhofer and Robert F. Tobler

A framework for real-time application of view-independent pre-calculated global-illumination solutions, retaining the ability to adjust the intensity of light-sources after pre-calculation, is described. High dynamic range scenes are fully supported. The framework is highly flexible both in terms of light-source numbers and target hardware: both high-end graphics-cards and older models are supported. Furthermore it is orthogonal to the global-illumination solution method and the chosen tonemapping operator, and therefore easy to implement into existing applications. Implementation details to both minimize memory footprint and maximize performance and flexibility are given. The performance of this framework has been evaluated in the context of an existing CAD application.

REAL-TIME RENDERING OF HIGH QUALITY GLARE IMAGES USING VERTEX TEXTURE FETCH ON GPU

Hidetoshi Ando, Nobutaka Torigoe, Koji Toriyama and Koichi Ichimiya

Using recent graphics hardware called GPU (Graphics Processing Unit), we can render high quality photorealistic images in real-time today. When rendering the scene, it is important to take into account how human eyes percept the whole scene. Glare is a phenomenon whereby bright light source cause spreading of light, and this effect is widely used in computer graphics to enhance reality of brightness of the scene. Real-time rendering of glare images is very important for recent computer games and virtual reality environment. Current technology for high quality glare rendering is too slow to be used for interactive applications, and fast rendering technology is limited to generate only blurry glare images. In this paper we introduce new technique for rendering high quality glare images in real-time using the latest technology called vertex texture fetch. The basic idea is to put what we call degenerate polygons on the screen as sensors to detect bright pixels and expand those polygons to form glare polygons where glare images are put. Combined with some performance enhancement techniques, our method can render very high quality glare images as fast as 60fps using modern GPU. We expect this new technology to be used widely in the next generation game consoles and PC games with modern GPU.

MOTION MAP GENERATION FOR MAINTAINING THE TEMPORAL COHERENCE OF BRUSH STROKES

Youngsup Park and KyungHyun Yoon

Painterly animation is a method that expresses images with a handpainted appearance from a video, and the most crucial element for it is the coherence between frames. A motion map generation is proposed in this paper as a resolution to the issue of maintaining the coherence in the brush strokes between the frames. A motion map refers to the range of motion calculated by their magnitudes and directions between the frames with the edge of the previous frame as a point of reference. The different methods of motion estimation used in this paper include the optical flow method and the block-based method, and the method that yielded the biggest PSNR using the motion information (the directions and magnitudes) acquired by various methods of motion estimation has been chosen as the final motion information to form a motion map. The created motion map determined the part of the frame that should be re-painted. In order to maintain the temporal coherence, the motion information was applied to only the strong edges that determine the directions of the brush strokes. Also, this paper sought to reduce the flickering phenomenon between the frames by using the multiple exposure method and the difference map created by the difference between images of the source and the canvas. Maintenance of the coherence in the direction of the brush strokes was also attempted by a local gradient interpolation in an attempt to maintain the structural coherence.

INTERACTION BETWEEN WATER AND DYNAMIC SOFT BODIES

Tatiana Alexandrova, Olivier Terraz and Djamchid Ghazanfarpour

The water animation by moving soft bodies, changing their shapes, is the subject of the present work. The mechanism of movement transformation from a body to a liquid is elaborated on the basis of Lattice-Boltzmann method of fluid modeling. The use of boundary conditions, destined to perform this transformation visually realistic and computationally quite inexpensive, is one of the main innovations of our approach. The model is applied to the jellyfish propulsion water.

AN EFFICIENT TEXTURE GENERATION TECHNIQUE FOR HUMAN HEAD CLONING AND MORPHING

Yu Zhang

This paper presents a technique to efficiently generate a parameterized full-head texture from a single face image of the scanned data for modeling photorealistic 3D heads. We automatically register face scans in a database by deforming a generic head mesh to fit the specific person's face geometry with a volume morphing approach. After the face texture is transferred onto it, the 3D generic mesh is parameterized over a 2D texture domain to establish a correspondence between all the scanned textures. After having performed a vertex-to-image binding for all vertices of the head mesh, we automatically generate a full-head texture using color interpolation for unbound regions and weighted average splines for visual boundary removal. We also use a deformation method to extract ear textures from the input image for texturing individual ears. With the exception of the initial feature point selection, our method is fully automated. We show photorealistic and real-time head rendering and morphing with the resulting texture.

VISUAL SIMULATING DICHROMATIC VISION IN CIE SPACE

Yinghua Hu

Dichromatic vision is due to the loss of one of the three cone pigments: the L type in protanopes, the M type in deuteranopes, and the S type in tritanopes. In this paper, I show that the dichromatic vision can be simulated by applying transformation to image in CIE x, y chromaticity space. I base my work on the past experiments on unilateral color blind (color blind in one eye) people which show that for protanopes and deuteranopes the hue of 470 nm and 575 nm stimuli stay the same as that for normal eyes, and for tritanopes the hue of 485 nm and 660 nm are the same as that for normal eyes. I also assume that the hue line between the anchored stimuli points in the chromaticity diagram is a quadratic curve passing though D6500 standard white stimuli. My method saves the steps for transformation of CIE chromaticity value to uniform chromaticity value or LMS value as required in the previous work and still gets reasonable results.

REALISTIC SIMULATION OF OCEAN SURFACE USING WAVE SPECTRA

Jocelyn Fréchot

We present a method to simulate ocean surfaces away from the coast, with correct statistical wave height and direction distributions. By using classical oceanographic parametric wave spectra, our results fit real world measurements, without depending on them. Since wave spectra are independent of the ocean model, Gerstner parametric equations and Fourier transform method can be used with them. Moreover, they are simple to use and need very few parameters. We explain how to accurately sample them, to achieve oceanic waves in deep water according to given wind parameters, in a realistic way.

TOWARDS VISUAL-BANDWIDTH: GETTING CLOSE TO ONE’S EXPERIMENT DATA

Mark R. Titchener

This paper presents the developments of a novel general purpose visualisation environment SPOD (Space Odyssey), that has evolved in relation to research needs. Our research is generally about the analysis and measurement of chaos and complexity in time-series data, and more specifically in deriving sleep state information from EEG/EOG. SPOD operates essentially as an interpreter of formated data files, to display surfaces, static and/or animated line and point graphs, in a virtual 3-D viewing space. It comfortably handles surfaces of more than 100,000 vertexes, and combinations of more than 15,000 static and/or animated graphs. User controls allow dynamic changes to viewing angle, lighting and display parameters. SPOD is ideally suited to ‘scoping’ experiment data and results, for visually debugging complex processing algorithms, or simply providing visual insight into complex data sets.

A NEW METHOD FOR BUILDING LARGE-FORMAT TILED DISPLAYS SYSTEMS

Sun Hanxu, Song Jingzhou, Jia Qingxuan, Gao xin, Yao Fusheng and Cheng Tao

Large-format tiled display is a new emerging technology for constructing large scale，high-resolution, immersive multi-projection virtual environment systems, which can present high-resolution stereo images. A PC-cluster, five- -display-channel tiled display system is built in this paper. It produces a 5120x768 stereo image. The software infrastructure has been designed using a retained mode sort-first parallel rendering paradigm. This paper discusses development issues including selecting on projectors and projection surface to support passive stereo, synchronization tiled displays, geometric correction and color calibration etc. Finally, overall display performance is given and future work is mentioned.

INTERACTIVE MEDIA AND DESIGN EDITING FOR LIVE VISUALS APPLICATIONS

Pascal Müller, Simon Schubiger-Banz, Stefan Müller Arisona and Matthias Specht

This paper describes novel concepts for the interactive composition of artistic real-time graphics, so-called live visuals. By establishing two fundamental techniques dealing with the structured media integration and the intrinsic design process, we significantly increase the efficiency of interactive editing in live visuals applications. First, we present a media manager that supports the user in both retrieval and utilization of automatically annotated digital media. The computer-assisted application of individual media items permits the interactive control of non-linear editing (NLE) of video in real-time. Second, we optimize the design process by introducing the design tree, which collects and organizes the artist’s work in an intuitive way. Design tree operations provide interactive high-level editing methods which allow for exploration, combination, reuse, and evolution of designs before and particularly during the performance. We examined the effectiveness of our techniques on numerous long-lasting live performances from which representative examples are demonstrated.

NiMMiT: A NOTATION FOR MODELING MULTIMODAL INTERACTION TECHNIQUES

Davy Vanacken, Joan De Boeck, Chris Raymaekers and Karin Coninx

In the past few years, multimodal interaction is gaining importance in virtual environments. Although multimodality makes interaction with the environment more intuitive and natural for the user, the development cycle of such an environment is often a long and expensive process. In our overall field of research, we investigate how model-based design can help shorten this process by designing the application with the use of high-level diagrams. In this scope, we present ‘NiMMiT’, a graphical notation, suitable for expressing multimodal user interaction. In this paper, we elaborate on the NiMMiT primitives, and afterwards a comprehensive example illustrates the notation in practice.

MIXED REALITY FOR EXPLORING URBAN ENVIRONMENTS

Fotis Liarokapis, David Mountain, Stelios Papakonstantinou, Vesna Brujic-Okretic and Jonathan Raper

In this paper we propose the use of a particular mobile system architecture for navigating into urban environments. The aim of this work is to evaluate how virtual and augmented reality interfaces can provide location and orientation-based services using different technologies. The virtual reality interface is entirely based on sensors to detect the location and orientation of the user while the augmented reality interface uses computer vision techniques to capture patterns form the real environment. The knowledge obtained from the evaluation of the virtual reality experience has been incorporated into the augmented reality interface. Some initial results in our experimental augmented reality navigation are presented.

SPHERE–TREES GENERATION AS NEEDED IN REAL TIME

Marta Franquesa Niubó and Omar Rodríguez González

In this paper two improvements to speed up collision detection are described. Firstly, a method called oncollide sphere-tree, OCST for short, is presented. This approach works by detecting collisions among models with arbitrary geometry using the video card’s Graphics Processing Units, GPU. While candidate parts of colliding objects are being detected, the OCST is constructed for collision evaluation in parallel, at the same time. Thus, the OCST is created in real–time. Secondly, we have tested two kinds of triangulated representation models for the same original–objects. We have evaluated triangle–soup and triangle–strip models to speed up the algorithm response when computing collisions. The method has been described, implemented and tested for the two kinds of triangulated models, and the obtained results are shown.

SYSTEM ARCHITECTURE OF A MIXED REALITY FRAMEWORK

Helmut Seibert and Patrick Dähne

In this paper the software architecture of a framework which simplifies the development of applications in the area of Virtual and Augmented Reality is presented. It is based on VRML/X3D to enable rendering of audio-visual information. We extended our VRML rendering system by a device management system that is based on the concept of a data-flow graph. The aim of the system is to create Mixed Reality (MR) applications simply by plugging together small prefabricated software components, instead of compiling monolithic C++ applications. The flexibility and the advantages of the presented framework are explained on the basis of an exemplary implementation of a classic Augmented Reality application and its extension to a collaborative remote expert scenario.

VIEWPOINT QUALITY AND GLOBAL SCENE EXPLORATION STRATEGIES

Dmitry Sokolov, Dimitri Plemenos and Karim Tamine

Virtual worlds exploration techniques are used in a wide variety of domains --- from the graph drawing to the robot motion. This paper is dedicated to virtual world exploration techniques which have to help a human being to understand a 3d scene. An improved method of a viewpoint quality estimation is presented in the paper, together with a new method for an automatic 3D scene exploration, based on a virtual camera. The automatic exploration method is related to off-line exploration and is made in two steps. In the first step, a ``global'' view of a scene is computed by determining a set of ``good'' points of view. The second step uses this set of points of view to compute a camera path around the scene.

DISTRIBUTED 3D INFORMATION VISUALIZATION - Towards Integration of the dynamic 3D graphics and Web Services

Dean Vucinic, Danny Deen, Emil Oanta, Zvonimir Batarilo and Chris Lacor

This paper focuses on visualization and manipulation of graphical content in distributed network environments. The developed graphical middleware and 3D desktop prototypes were specialized for situational awareness. This research was done in the LArge Scale COllaborative decision support Technology (LASCOT) project, which explored and combined software technologies to support human-centred decision support system for crisis management (earthquake, tsunami, flooding, airplane or oil-tanker incidents, chemical, radio-active or other pollutants spreading, etc.). The performed state-of-the-art review did not identify any publicly available large scale distributed application of this kind. Existing proprietary solutions rely on the conventional technologies and 2D representations. Our challenge was to apply the "latest" available technologies, such Java3D, X3D and SOAP, compatible with average computer graphics hardware. The selected technologies are integrated and we demonstrate: the flow of data, which originates from heterogeneous data sources; interoperability across different operating systems and 3D visual representations to enhance the end-users interactions.

URBAN CITY PLANNING IN SEMI-IMMERSIVE VIRTUAL REALITY SYSTEMS

Frank Steinicke, Timo Ropinski, Klaus Hinrichs and Jörg Mensmann

Virtual reality based geographic information systems (VRGIS) have been successfully employed for urban planning and architectural design in recent years. Tracking technologies and stereoscopic visualization of three-dimensional structures allow a better insight into complex datasets. Unfortunately, these systems often lack intuitive interaction concepts and therefore reduce VRGIS to advanced visualization environments, since manipulations of the content is not or only rudimentarily possible. In this paper, we present a geographic information system for urban planning tasks in semi-immersive virtual reality (VR) systems. The objective of this approach is to provide professional city planners with an enhanced VR interface, which enables com- fortable interaction concepts similar to the interactions of the real-world planning task. To assure the usability and relevance of the developed system, urban planners have cooperated closely in the development process. In this paper both the hard- and software architecture of the entire system as well as VR related interaction metaphors and their evaluation are discussed.

EMG AS A DAILY WEARABLE INTERFACE

Tiago João Vieira Guerreiro and Joaquim Armando Pires Jorge

We present electromyography as an interface to control computer applications. Our prototype makes possible for users to control any application through muscle contractions. Electromyographic device portability and the monitoring possibility for any muscle voluntarily contracted can bring great benefits at the mobility level as in accessibility issues. Through operating system events emulation and their association with determined muscle contractions we can replace the pointing device or some keyboard elements, achieving control of any application. Usability evaluations validate electromyography as a daily wearable interface where we show that it can be used even in a mobility context. Considering accessibility, we present a synergy between applications that ease message writing. Evaluations show that this synergy outperforms existent text-entry interfaces, based on point and click approaches.

DANCE EVALUATION SYSTEM BASED ON MOTION ANALYSIS

Masahiro Tada and Masahide Naemura

We are conducting research on computer-aided edutainment with a view toward creating learning environments where anybody can acquire advanced skills. In this paper, we focus on dance actions as a part of edutainment research and propose a method to evaluate dance skills through motion analysis. Our method consists of wavelet multi-resolution analysis and correlation analysis. Firstly, by using wavelet multi-resolution analysis, we decompose complex dance motion data acquired from a motion-capture system into different frequency components. And by applying correlation analysis to the decomposed data, we extract motion features that play a dominant role in evaluating sense of rhythm and harmony of movement of each body part. By comparing the extracted features of amateurs to those of experts, we have achieved a quantitative evaluation method for dance skills. Through experiments, we confirmed that there is a strong correlation amongst extracted motion features and subjective evaluation results of dance skills. Using the proposed method, we have developed a computer-aided edutainment system for dance. By mapping motion-captured dance data and its evaluation results onto the 3-D CG figure, our system enables users to visually know bad points of their dance and acquire more advanced dance skills.

A BASIC GESTURE AND MOTION FORMAT FOR VIRTUAL REALITY MULTISENSORY APPLICATIONS

Annie Luciani, Matthieu Evrard, Damien Couroussé, Nicolas Castagné, Claude Cadoz and Jean-Loup Florens

The question of encoding movements as those produced by human gestures may become central in the coming years, given the growing importance of movement data exchanges between heterogeneous systems and applications (musical applications, 3D motion control, virtual reality interaction, etc.). For the past 20 years, various formats have been proposed for encoding movement, especially gestures. Though, these formats, at different degrees, were designed in the context of quite specific applications (character animation, motion capture, musical gesture, biomechanical concerns…). The article introduce a new file format, called GMS for ‘Gesture and Motion Signal’, with the aim of being more low level and generic, by defining the minimal features a format carrying movement/gesture information needs, rather than by gathering all the information generally given by the existing formats. The article argues that, given its growing presence in virtual reality situations, the “gesture signal” itself must be encoded, and that a specific format is needed. The proposed format features the inner properties of such signals: dimensionality, structural features, types of variables, and spatial and temporal properties. The article first reviews the various situations with multisensory virtual objects in which gesture controls intervene. The proposed format is then deduced, as a mean to encode such versatile and variable “gestural and animated scene”.